test: Remove export from the tests, language, and libraries. rs=deexporting
rustc: make integral type inference transactional, close #3211, close #4401, close #3398.
test: fix compile-fail tests somehow missed from local 'make check', r=burningtree.
librustc: Remove legacy exports from the language. r=brson
rustdoc: Various bits of modernization
rustdoc: deny(deprecated_mode)
rustdoc: Stop using a custom error handler. Closes #4698
rustdoc: De-mode
rustdoc: Remove structural records
librustc: Change `self` as a type to `Self` everywhere. r=brson
rustdoc: deny(deprecated_self)
wip